Abstract: Different concentrations（0，40，80，120，160，200 mmol/L）of MgCl₂ solution were set up to study the effects of MgCl₂ stress on the seed germination，seedling growth and physiological indexes of alfalfa.The gray correlation analysis was used to screen the salt tolerance indexes，with the aim of providing a certain theoretical basis for the research on the response mechanism of alfalfa to MgCl₂ stress and the governance of saline‑alkali land. The results showed that with the increase of MgCl₂ concentration and treatment time，the inhibition of alfalfa seed germination and seedling growth became more and more severe.When the MgCl₂ concentration was 200 mmol/L，the seeds did not germinate and the salt damage index was 1.0.Among the germination indexes of alfalfa seeds，the fresh weight，germination rate and germination index were more closely related to salt tolerance，with correlation degrees of 0.948，0.927 and 0.927，respectively.Among the seedling growth and physiological indexes，the chlorophyll content，superoxide dismutase（SOD） activity and catalase（CAT） activity were more closely related to salt tolerance，with correlation degrees of 0.941，0.920 and 0.917，respectively. In conclusion，the main salt tolerance indexes of alfalfa are fresh weight，germination rate，germination index and chlorophyll content，SOD activity，CAT activity at germination and seedling stages，respectively.

Key words: Alfalfa, MgCl₂, Germination of seeds, Seedling growth, Salt tolerance indexes

摘要： ：设置不同浓度（0、40、80、120、160、200 mmol/L）MgCl₂溶液，研究MgCl2胁迫对紫花苜蓿种子萌发和幼苗生长、生理指标的影响，并采用灰色关联度分析法筛选耐盐指标，以期为紫花苜蓿响应MgCl₂胁迫的应答机制研究及盐碱地治理提供一定的理论基础。结果表明，随着MgCl₂浓度增加、处理时间延长，紫花苜蓿种子萌发、幼苗生长受到的抑制程度越来越大，在MgCl₂浓度为200 mmol/L时，种子不萌发，盐害指数为1.0。紫花苜蓿种子萌发指标中与耐盐性关联较大的指标是鲜质量、发芽率和发芽指数，关联度分别为0.948、0.927和0.927；苗期生长、生理指标中与耐盐性关联较大的指标是叶绿素含量、超氧化物歧化酶（SOD）活性和过氧化氢酶（CAT）活性，关联度分别为0.941、0.920和0.917。综上，紫花苜蓿萌发期和苗期的主要耐盐指标分别为鲜质量、发芽率、发芽指数和叶绿素含量、SOD活性、CAT活性。

关键词: 紫花苜蓿, MgCl₂, 种子萌发, 幼苗生长, 耐盐指标